Description and Design Goals

Our design is a novel high-gain, high-speed, low-noise transimpedance amplifier based on a resistive feedback op amp design. Our design leverages differential sensing of the photodiode, allowing for a truly differential circuit design without duplicating the optical signals. Our goals are to have a low enough noise floor to enable persistence of quantum data while amplifying signals to measurable levels (high-gain). With these goals being met, the intent is to maximize amplifier speed. This top-level TIA design and the core op-amp will be very valuable to the open-source community. However, this circuit has been designed for integration with photonic ICs to enable QRNG.

Quantum Random Number Generation (QRNG) uses the inherent randomness of quantum mechanics to produce random numbers which are information-theoretically provable, truly random (as opposed to pseudorandom), and pass existing standard benchmarks. On-chip QRNG has been done before; however, what makes this project unique is that we use a 90° optical hybrid and have moved the detector circuit (TIA) from an external PCB to silicon, improving performance of the system. Both advances will allow for future research beyond QRNG into other useful quantum information such as quantum state tomography, quantum key distribution (QKD), and more.

This second version of the design has increased resistance in its feedback resistor and uses deep nwells in the output buffer, to increase gain by 16dB from the previos design (sacrificing some speed).

Performance Summary

Gain: 112dB

Bandwidth: 10MHz

Noise: 20nArms

Dynamic Range: 50dB

Block Diagram

Schematics

References

Y. Fujimoto, H. Tani, M. Maruyama, H. Akada, H. Ogawa and M. Miyamoto, "A low-power switched-capacitor variable gain amplifier," in IEEE Journal of Solid-State Circuits, vol. 39, no. 7, pp. 1213-1216, July 2004, doi: 10.1109/JSSC.2004.829919.

E. Kang et al., "A Variable-Gain Low-Noise Transimpedance Amplifier for Miniature Ultrasound Probes," in IEEE Journal of Solid-State Circuits, vol. 55, no. 12, pp. 3157-3168, Dec. 2020, doi: 10.1109/JSSC.2020.3023618.

U. Anusha, S. Raghu and P. Duraiswamy, "30-Gb/s low power inductorless CMOS transimpedance amplifier for optical receivers," 2018 3rd International Conference on Microwave and Photonics (ICMAP), 2018, pp. 1-2, doi: 10.1109/ICMAP.2018.8354482.

J. Jin and S. S. H. Hsu, "A 40-Gb/s Transimpedance Amplifier in 0.18-$\mu$m CMOS Technology," in IEEE Journal of Solid-State Circuits, vol. 43, no. 6, pp. 1449-1457, June 2008, doi: 10.1109/JSSC.2008.922735.

Francesco Raffaelli, Giacomo Ferranti, Dylan H Mahler, Philip Sibson, Jake E Kennard, Alberto Santamato, Gary Sinclair, Damien Bonneau, Mark G Thompson and Jonathan C F Matthews, “A homodyne detector integrated onto a photonic chip for measuring quantum states and generating random numbers”, Quantum Science and Technology, vol. 3, no. 2. Feb. 2018. https://iopscience.iop.org/article/10.1088/2058-9565/aaa38f

Team Members

Lead Designer:

Jared Marchant – Ph.D Student – Micropower Circuits Lab – Brigham Young University  - USA

Role: Lead circuit designer

Sarah Maia – Undergraduate Student Sophomore – CamachoLab – Brigham Young University - Brazil

Role: High-level SPICE simulations, QRNG theory and verification

Topher Eyre – High School Student – CamachoLab - Male - USA

Role: SPICE simulations, layout

Sequoia Ploeg – Master’s Student – CamachoLab – Brigham Young University  - USA

Role: Photonic Chip Design

Christian Carver – Master’s Student – CamachoLab – Brigham Young University - USA

Role: Quantum Engineering, Photonic Design

Dr. Shiuh-hua Wood Chiang – Associate Professor – Micropower Circuits Lab - Brigham Young University - USA

Role: Low-Power RF/Analog/Mixed-Signal Circuits for Communications and Sensing Applications

Dr. Ryan Camacho – Associate Professor – CamachoLab – Brigham Young University - USA

Role: Micro and Nano Optical Structures, Quantum Engineering